I think the hierarchy was Interval, Expert, Master, and Prevail, with Prevail being the highest. There might have been a Momentum in there, too. Not sure when the Prevail was introduced, but it used Prestige tubing. Diamondback's manufacturer eventually moved to tig-welded Tange OS, then TrueTemper RC heat treated tubing for the 3 bikes. I built up a pink Master TG for my girlfriend.

A link to RobbieTunes's post on this topic